U.S. patent number 9,788,803 [Application Number 14/233,337] was granted by the patent office on 2017-10-17 for medical-data processing device and radiation tomography apparatus having the same.
This patent grant is currently assigned to SHIMADZU CORPORATION. The grantee listed for this patent is Ayako Akazawa, Junichi Ohi, Yoshiyuki Yamakawa. Invention is credited to Ayako Akazawa, Junichi Ohi, Yoshiyuki Yamakawa.
United States Patent |
9,788,803 |
Ohi , et al. |
October 17, 2017 |
Medical-data processing device and radiation tomography apparatus
having the same
Abstract
The disclosure has an object to provide a medical-data
processing device that allows generation of an MIP image suitable
for diagnosis. With the medical-data processing device of the
disclosure, intensity of a body surface region in three-dimensional
space data is adjusted. The body surface region corresponds to a
body surface of a stereoscopic image of a subject. Since the
intensity of the body surface region is adjusted to be decreased,
the maximum intensity is selected from a portion except for the
body surface region to generate the MIP image. This prevents the
body surface of the subject from appearing upon generating the MIP
image. Therefore, the MIP image is obtainable having excellent
visibility to the inside of the subject.
Inventors: |
Ohi; Junichi (Muko,
JP), Yamakawa; Yoshiyuki (Uji, JP),
Akazawa; Ayako (Kyotanabe, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Ohi; Junichi
Yamakawa; Yoshiyuki
Akazawa; Ayako |
Muko
Uji
Kyotanabe |
N/A
N/A
N/A |
JP
JP
JP |
|
|
Assignee: |
SHIMADZU CORPORATION
(Kyoto-Shi, Kyoto, JP)
|
Family
ID: |
47882725 |
Appl.
No.: |
14/233,337 |
Filed: |
September 15, 2011 |
PCT
Filed: |
September 15, 2011 |
PCT No.: |
PCT/JP2011/005223 |
371(c)(1),(2),(4) Date: |
January 16, 2014 |
PCT
Pub. No.: |
WO2013/038452 |
PCT
Pub. Date: |
March 21, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20140135622 A1 |
May 15, 2014 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
6/027 (20130101); A61B 6/502 (20130101); A61B
6/037 (20130101); A61B 6/5223 (20130101); A61B
6/022 (20130101) |
Current International
Class: |
A61B
6/00 (20060101); A61B 6/03 (20060101); A61B
6/02 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2005-106507 |
|
Apr 2005 |
|
JP |
|
2007/100955 |
|
Sep 2007 |
|
WO |
|
2009/066195 |
|
May 2009 |
|
WO |
|
2009/153860 |
|
Dec 2009 |
|
WO |
|
Other References
International Search Report issued in International Application No.
PCT/JP2011/005223 dated Dec. 6, 2011. cited by applicant.
|
Primary Examiner: Smith; Ruth S
Attorney, Agent or Firm: McDermott Will & Emery LLP
Claims
The invention claimed is:
1. A medical-data processing device for processing
three-dimensional space data outputted from a tomographic
apparatus, the medical-data processing device comprising: a
body-surface identifying device configured to identify a body
surface region by performing contour extraction process to the
three-dimensional space data, the body surface region corresponding
to a body surface of a stereoscopic image of a subject; an
intensity adjusting device configured to adjust intensity of the
body surface region in the three-dimensional space data; and an
image generating device configured to generate a maximum-intensity
projection image in accordance with the three-dimensional space
data having the intensity adjusted, wherein the intensity adjusting
device decreases the intensity of the body surface region, whereby
the image generating device generates the image by selecting the
maximum intensity from a portion of the three-dimensional space
data except for the body surface region.
2. The medical-data processing device according to claim 1, wherein
the intensity adjusting device operates relative to the body
surface region identified by the body-surface identifying
device.
3. The medical-data processing device according to claim 1, wherein
the body-surface identifying device detects a boundary of the
stereoscopic image of the subject and a void where no subject
appears in the three-dimensional space data in accordance with
whether or not the intensity of each voxel constituting the
three-dimensional space data exceeds a threshold.
4. A radiation tomography apparatus, comprising: a detector ring
configured to detect radiation emitted from a subject; a space data
generating device configured to generate three-dimensional space
data containing a stereoscopic image of the subject in accordance
with output from the detector ring; a body-surface identifying
device configured to identify a body surface region by performing
contour extraction process to the three-dimensional space data, the
body surface region corresponding to a body surface of the
stereoscopic image of the subject; an intensity adjusting device
configured to adjust intensity of the body surface region in the
three-dimensional space data; and an image generating device
configured to generate a maximum-intensity projection image in
accordance with the three-dimensional space data having the
intensity adjusted, wherein the intensity adjusting device
decreases the intensity of the body surface region, whereby the
image generating device selects the maximum intensity from a
portion other than the body surface region in the three-dimensional
space data to generate the image.
5. The radiation tomography apparatus according to claim 4, wherein
the intensity adjusting device operates relative to the body
surface region identified by the body-surface identifying
device.
6. The radiation tomography apparatus according to claim 4, wherein
the body-surface identifying device detects a boundary of the
stereoscopic image of the subject and a void where no subject
appears in the three-dimensional space data in accordance with
whether or not the intensity of each voxel constituting the
three-dimensional space data exceeds a threshold.
7. The radiation tomography apparatus according to claim 4, wherein
the subject is a breast.
Description
RELATED APPLICATIONS
This application is the U.S. National Phase under 35U.S.C.
.sctn.371, of International Application No. PCT/JP2011/005223,
filed on Sep. 15 2011, the disclosure of which Application is
incorporated by reference herein.
TECHNICAL FIELD
The present invention relates to a medical-data processing device
configured to generate an MIP (maximum-intensity projection) image
and a radiation tomography apparatus having the medical-data
processing device.
BACKGROUND ART
A medical institution is equipped with a radiation tomography
apparatus for picking up tomographic images of a subject with
radiation. Examples of such a radiation tomography apparatus
include a PET (Positron Emission Tomography) apparatus configured
to image radiopharmaceutical distribution within a subject. See,
for example, Japanese Patent Publication (Translation of PCT
Application) No. 2009-528139A.
Data obtained with the PET apparatus is three-dimensional data
representing distribution intensity of radiopharmaceutical
three-dimensionally. MIP imaging is one method of representing the
three-dimensional data simply and conveniently as a two-dimensional
image.
Description will be given of generating an MIP image.
Three-dimensional data obtained with the PET apparatus contains a
stereoscopic image of a subject. Here, a plane F relative to the
stereoscopic image is to be considered. Next, a line N is to be
considered. The line N passes through the plane F vertically and
passes through the stereoscopic image V. See FIG. 10. The plane F
is drawn as a line in FIG. 10 since the plane F is orthogonal to
the plane of FIG. 10.
Here, considered is one of voxels of the stereoscopic image V on
the line N. The voxel is a constitutional unit of three-dimensional
data and corresponds to a pixel of a two-dimensional image. The
voxel on the line N having the highest intensity corresponds to the
maximum intensity of the line N.
The MIP image is obtained by placing the maximum intensity of the
line N on an intersection Q of the line N and the plane F. That is,
the maximum intensity of a plurality of lines parallel to the line
N passing through the plane F is selected and placed successively,
whereby an MIP image is generated. The MIP image generated in this
way is an image with a remarkable configuration in the stereoscopic
image V projected on the plane F.
Diagnosis with the MIP image allows rough determination of a
portion of the subject where radiopharmaceutical concentrates. When
the subject has inside thereof a concentrated portion of the
radiopharmaceutical, it is determined that voxels with high
intensity are collected in a portion of the three-dimensional data
corresponding to the concentrated portion. The MIP image is
generated while such the high intensity of the voxels is collected.
Accordingly, diagnosis with the MIP image allows simple and
convenient determination of a portion with high intensity in the
three-dimensional data.
SUMMARY OF INVENTION
Technical Problem
The conventional construction as above, however, has the following
problem.
Specifically, with the conventional construction, a body surface of
a subject is obstructive to generation of the MIP image. Such a
problem may arise. Radiopharmaceutical used in the PET apparatus
has a tendency of concentrating in skin (body surface) of the
subject. As the radiopharmaceutical, such a chemical compound that
concentrates in cancer tissues is selected. Accordingly, a portion
where the radiopharmaceutical concentrates may be more likely
cancer tissues. On the other hand, the radiopharmaceutical also
concentrates in normal tissues, for example, of the body
surface.
Consequently, the radiopharmaceutical concentrates also in the body
surface of the subject image in the three-dimensional data obtained
with the PET apparatus. Diagnosis with the PET apparatus has a
purpose of determining presence of cancer tissues inside the body
surface. Therefore, the radiopharmaceutical concentrating on the
body surface of the subject is obstructive to diagnosis.
Description will be given in detail of influences of the body
surface of the subject. Upon generating the MIP image from the
three-dimensional data, the voxel corresponding to the body surface
of the subject may sometimes be of the maximum intensity on the
line N. In this case, the body surface of the subject as normal
tissues is projected on the MIP image to mask distribution of the
radiopharmaceutical within the subject. Radiopharmaceutical with
far higher concentration than that on the body surface may
concentrate inside the body surface. However, with the conventional
method of generating the MIP image, no concentrated portion of
radiopharmaceutical as above is projected in the MIP image. Taking
into consideration that the concentrated portion of
radiopharmaceutical may be cancer tissues, cancer tissues other
than skin cancer and cancer reaching the skin may be overlooked
with the conventional method.
The present invention has been made regarding the state of the art
noted above, and its object is to provide a medical-data processing
device and a radiation tomography apparatus having the medical-data
processing device that allows generation of an MIP image more
suitable for diagnosis.
Solution to Problem
The present invention adopts the following construction for
overcoming the above problem. One aspect of the present invention
discloses a medical-data processing device for processing
three-dimensional space data outputted from a tomographic
apparatus. The medical-data processing device includes a
body-surface intensity adjusting device configured to adjust
intensity of a body surface region in the three-dimensional space
data, the body surface region corresponding to a body surface of a
stereoscopic image of a subject; and a maximum-intensity projection
image generating device configured to generate a maximum-intensity
projection image in accordance with the three-dimensional space
data having the intensity adjusted. The body-surface intensity
adjusting device decreases the intensity of the body surface
region, whereby the maximum-intensity projection image generating
device generates the image by selecting the maximum intensity from
a portion of the three-dimensional space data except for the body
surface region.
Operation and Effect
With the medical-data processing device according to the aspect of
the present invention, the intensity of the body surface region in
the three-dimensional space data is adjusted, the body surface
region corresponding to the body surface of the stereoscopic image
of the subject. The intensity of the body surface region is
adjusted to be decreased. Consequently, the maximum intensity is
selected from the portion except for the body surface region to
generate the maximum-intensity projection image (MIP image). This
avoids appearance of the body surface of the subject upon
generating the MIP image. Accordingly, the MIP image is obtainable
having excellent visibility to the inside of the subject.
Moreover, it is preferable that the medical-data processing device
further includes a body-surface identifying device configured to
identify the body surface region by performing contour extraction
process to the three-dimensional space data, and that the
body-surface intensity adjusting device operates relative to the
body surface region identified by the body-surface identifying
device.
Operation and Effect
The above construction is a detailed construction of the
medical-data processing device according to the present invention.
As noted above, the contour extraction process is performed to the
three-dimensional space data to identify the body surface region.
This achieves accurate determination of the body surface region.
Consequently, the construction ensured to generate the MIP image
with excellent visibility.
Moreover, it is more preferable that the body-surface identifying
device of the medical-data processing device detects a boundary of
the stereoscopic image of the subject and a void where no subject
appears in the three-dimensional space data in accordance with
whether or not the intensity of each voxel constituting the
three-dimensional space data exceeds a threshold.
Operation and Effect
The above construction is a detailed construction of the
medical-data processing device according to the present invention.
As noted above, the body surface region is identified with use of
the threshold, resulting in accurate determination of the body
surface region. Consequently, such the construction ensures to
generate the MIP image with excellent visibility.
The present invention also has disclosure relating to a radiation
tomography apparatus having a function of the medical-data
processing device. That is, another aspect of the present invention
discloses a radiation tomography apparatus. The radiation
tomography apparatus includes a detector ring configured to detect
radiation emitted from a subject; a space data generating device
configured to generate three-dimensional space data containing a
stereoscopic image of the subject in accordance with output from
the detector ring; a body-surface intensity adjusting device
configured to adjust intensity of a body surface region in the
three-dimensional space data, the region corresponding to a body
surface of the stereoscopic image of the subject; and a
maximum-intensity projection image generating device configured to
generate a maximum-intensity projection image in accordance with
the three-dimensional space data having the intensity adjusted. The
body-surface intensity adjusting device decreases the intensity of
the body surface region, whereby the maximum-intensity projection
image generating device selects the maximum intensity from a
portion other than the body surface region in the three-dimensional
space data to generate the image.
Moreover, it is preferable that the radiation tomography apparatus
includes a body-surface identifying device configured to identify
the body surface region by performing contour extraction process to
the three-dimensional space data, and that the body-surface
intensity adjusting device operates relative to the body surface
region identified by the body-surface identifying device.
Moreover, it is more preferable that the body-surface identifying
device of the radiation tomography apparatus detects a boundary of
the stereoscopic image of the subject and a void where no subject
appears in the three-dimensional space data in accordance with
whether or not the intensity of each voxel constituting the
three-dimensional space data exceeds a threshold.
Operation and Effect
The above construction allows provision of the radiation tomography
apparatus capable of obtaining the maximum-intensity projection
image representing accurately the inside of the subject with no
body surface of the subject appearing upon generating the MIP
image.
Moreover, it is preferable that the radiation tomography apparatus
is for breast inspection.
Operation and Effect
The above construction is a detailed construction of the radiation
tomography apparatus according to the present invention. Typically,
it is difficult to image breast cancer with radiopharmaceutical.
However, the present invention allows accurate breast inspection
since the MIP image faithfully representing the inside of the
subject is obtainable.
Advantageous Effects of Invention
In the medical-data processing device of the present invention, the
intensity in the body surface region in the three-dimensional space
data is adjusted, the region corresponding to the body surface of
the stereoscopic image of the subject. Since the intensity in the
body surface region is adjusted to be decreased, and thus the image
is generated by selecting the maximum intensity from the portion
except for the body surface region upon generating the MIP image.
This prevents the body surface of the subject from appearing upon
generating the MIP image. Consequently, the MIP image is obtainable
having excellent visibility to the inside of the subject.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a function block diagram of a medical-data processing
device according to one embodiment.
FIG. 2 is a schematic view illustrating space data according to the
embodiment.
FIGS. 3 to 6 are schematic views each illustrating a body-surface
identifying unit according to the embodiment.
FIG. 7 is a schematic view illustrating space data having corrected
intensity according to the embodiment.
FIG. 8 is a schematic view illustrating an MIP image generating
unit according to the embodiment.
FIG. 9 is a function block diagram illustrating a radiation
tomography apparatus according to another embodiment.
FIG. 10 is a schematic view of a conventional apparatus.
DESCRIPTION OF EMBODIMENTS
Description will be given hereinafter of embodiments with reference
to drawings.
Embodiment 1
<Whole Construction of Medical-Data Processing Device>
A medical-data processing device (hereinafter, simply referred to
as a data processor 8) according to Embodiment 1 outputs an MIP
image P1 upon receiving three-dimensional space data (hereinafter,
simply referred to as space data D1) containing a stereoscopic
image of a subject, as illustrated in FIG. 1. The space data D1 is
obtained by reconstructing raw data on a three-dimensional space
with various tomographic images, the raw data being obtained upon
radiography of a stereoscopic image of a subject. Examples of raw
data include sinogram or list data. The MIP image P1 corresponds to
the maximum-intensity projection image in the present invention.
The space data D1 corresponds to the three-dimensional space data
in the present invention.
In the space data D1, distribution of radiopharmaceutical within
the subject is expressed by intensity. A void in the space data D1
where no subject image appears has an intensity value lower than
that of a subject image. In addition, much radiopharmaceutical
concentrates in the skin of the subject image. This is because the
radiopharmaceutical has a tendency of concentrating not only in
cancer tissues but also in normal skin.
As illustrated in FIG. 1, the data processor 8 of Embodiment 1
includes a body-surface identifying unit 1. The body-surface
identifying unit 1 identifies a portion in the space data D1 by
performing contour extraction process to the space data D1. The
portion (a portion containing a body surface: a body surface region
R) corresponds to a body surface of the stereoscopic image of the
subject. In addition, the data processor 8 includes a body-surface
intensity adjusting unit 2 and an MIP image generating unit 3. The
body-surface intensity adjusting unit 2 adjusts the intensity of
the body surface region R in the space data D1. The MIP image
generating unit 3 generates an MIP image P1 in accordance with the
space data D1 having the adjusted intensity. The body-surface
identifying unit 1 corresponds to the body-surface identifying
device in the present invention. The body-surface intensity
adjusting unit 2 corresponds to the body-surface intensity
adjusting device in the present invention. The MIP image generating
unit 3 corresponds to the maximum-intensity projection image
generating device in the present invention.
As illustrated in FIG. 2, the space data D1 is three-dimensional
matrix data containing the stereoscopic image of the subject in the
three-dimensional space. The space data D1 has voxels in each of
which data (e.g., intensity) detected by the radiation tomography
apparatus is arranged. The space data D1 is obtained while the
subject is guided to a field of view of the radiation tomography
apparatus. The voxels are arranged within a space of a rectangular
solid to constitute the space data D1. The space data D1 is defined
as a rectangular solid since this shape is advantageous for holding
the data. The space data D1 of the rectangular solid contains
inside thereof the entire field of view of the radiation tomography
apparatus in a cylindrical shape. Here, the space data D1 is
illustrated as one example having an image of a breast B obtained
with a PET apparatus for breast inspection. In FIG. 2, a hatched
breast B represents skin of the breast B. The skin corresponds to
the body surface in the present invention.
As above, the space data D1 corresponds to the three-dimensional
reconstruction data prior to generation of the tomographic image
with the radiation tomography apparatus.
Description will be given of operations of the body-surface
identifying unit 1. The body-surface identifying unit 1 firstly
generates a tomographic image P0 obtained by slicing the space data
D1 along a virtual plane. Thus, a plurality of tomographic images
P0 is to be generated for a plurality of virtual planes parallel to
one another. The stereoscopic image of the subject is to be
separated into a plurality of tomographic images P0. FIG. 3
illustrates one of the tomographic images P0 generated with the
body-surface identifying unit 1.
Next, the body-surface identifying unit 1 generates a profile about
a line crossing the tomographic image P0. The profile has a
relationship between intensity and a position on the line. A
plurality of profiles is generated for a plurality of lines
parallel to one another. Thus, the tomographic image P0 is
separated into a plurality of profiles. FIG. 4 illustrates one of
the profiles generated with the body-surface identifying unit 1.
Two peaks in FIG. 4 each represent a contact portion to the skin
(body surface) of the subject. Since radiopharmaceutical has a
property of concentrating on the body surface, a position in the
profile corresponding to the body surface has a high intensity
value.
The body-surface identifying unit 1 successively obtains intensity
of one end to the other end of the profile to identify positions
where the intensity exceeds a threshold p. Then, the body-surface
identifying unit 1 performs similar operation from the other end to
one end of the profile. FIG. 4 illustrates the positions identified
by the body-surface identifying unit 1 by arrows. Here, one end and
the other end of the profile each correspond to a void where no
subject image appears. The void has an intensity value lower than
that of the subject image, and is also called a background.
When the intensity value is seen from one end to the other end of
the profile step by step, a position appears where the intensity
becomes higher. Taking into consideration that the subject image
has an intensity value higher than the void, the void is shifted to
the subject image at this position. Thus, the body-surface
identifying unit 1 detects a boundary of the stereoscopic image of
the subject and the void where no subject appears in the space data
D1 by determining whether or not the intensity of each voxel
constituting the space data D1 exceeds the threshold.
Here, numeral s in FIG. 5 denotes the boundary of the subject image
and the void detected with the body-surface identifying unit 1. The
boundary s is detected by identifying a position where the
intensity exceeds the threshold p by the body-surface identifying
unit 1 in accordance with a plurality of profiles.
FIG. 6 illustrates identification of the body surface of the
subject by the body-surface identifying unit 1 in accordance with
the boundary s. The body-surface identifying unit 1 sets a body
surface region R having a given width from the boundary toward the
void. The body surface region R is also set so as to have a given
width from the boundary s toward the subject image. The width of
the body surface region R toward void is larger than that toward
the subject image. Accordingly, a portion of the body surface is
certainly removable. This ensures to remove a portion of the body
surface of the subject with high intensity. In FIG. 6, a U-shaped
area enclosed with dotted lines represents the body surface region
identified by the body-surface identifying unit 1.
The position of the body surface region R identified by the
body-surface identifying unit 1 is represented by position data H.
The position data H is sent to the body-surface intensity adjusting
unit 2. The body-surface intensity adjusting unit 2 recognizes a
position of the body surface region R in the space data D1 in
accordance with the position data H. Then, the body-surface
intensity adjusting unit 2 makes an intensity value of the voxel
within the body surface region R to 0. This causes elimination of
the body surface in the space data D1 with high intensity of the
stereoscopic image of the subject.
FIG. 7 illustrates three-dimensional space data
(intensity-corrected space data D2) generated by performing
intensity correction made by the body-surface intensity adjusting
unit 2 to the space data D1. The intensity-corrected space data D2
contains the subject image having the body surface removed
therefrom. The subject image in FIG. 7 has no body surface of the
subject (breast B) in FIG. 2, and thus the inside is exposed.
The intensity-corrected space data D2 is sent to the MIP image
generating unit 3 from the body-surface intensity adjusting unit 2,
as shown in FIG. 1. The MIP image generating unit 3 generates an
MIP image P1 in accordance with the intensity-corrected space data
D2. The MIP image P1 is to be described. As illustrated in FIG. 8,
the MIP (maximum-intensity projection) image is a two-dimensional
image when the intensity-corrected space data D2 is projected on a
plane F. The MIP image P1 is generated as under. Firstly, a plane F
where the MIP image P1 is to be generated and a line N orthogonal
to the plane F are assumed. Voxel data through which the line N
passes represents intensity. Here, the maximum intensity is
selected from the intensity, and is placed at a position in the
plane F through which the line N passes. In other words, the
maximum intensity is to be selected from any position on the dotted
line in FIG. 8 where the line N crosses a three-dimensional image
of the subject. This operation is performed to other positions in
the plane F, achieving obtainment of the MIP image P1 having the
maximum intensity in each line arranged two-dimensionally.
When the MIP image generating unit 3 generates the MIP image P1, no
intensity value at the position on the body surface of the subject
image appears in the MIP image. This is because the intensity on
the body surface of the subject is substituted for 0 in the
intensity-corrected space data D2, and thus the body surface of the
subject is eliminated from the data. Consequently, the MIP image P1
is an image containing the inside from the body surface.
In other words, the body-surface intensity adjusting unit 2
decreases the intensity of the body surface region R, whereby the
MIP image generating unit 3 generates the MIP image P1 by selecting
the maximum intensity from the portion except for the body surface
region R.
A main controller 27 is provided for performing control to each of
controllers en bloc. The main controller 27 has a CPU, and provides
each of the controllers 1, 2, and 3 by executing various programs.
A console 26 is provided for inputting operator's commands. A
memory unit 28 stores the threshold p used in the body-surface
identifying unit 1. A display unit 25 is provided for displaying
the generated MIP image P1.
As noted above, with the data processor 8 of the present invention,
the intensity of the body surface region R in the space data D1 is
adjusted, the region R corresponding to the body surface of the
stereoscopic image of the subject. Since the intensity of the body
surface region R is adjusted to be decreased, the maximum intensity
is selected from the portion except for the body surface region R
to generate the maximum-intensity projection image (MIP image P1).
This prevents the body surface of the subject from appearing upon
generating the MIP image P1. Consequently, the MIP image P1 is
obtainable having excellent visibility to the inside of the
subject.
Moreover, as noted above, the contour extraction process is
performed to the space data D1 to identify the body surface region
R, resulting in accurate determination of the body surface region
R. Therefore, the construction as above ensures to generate the MIP
image P1 having excellent visibility.
Furthermore, the body surface region R is identified as above with
the threshold p, resulting in accurate determination of the body
surface region R.
Embodiment 2
Next, an embodiment of a radiation tomography apparatus according
to the present invention will be described hereinafter with
reference to drawings. Gamma-rays in Embodiment 2 are one example
of the radiation in the present invention. Embodiment 2 discloses a
mammography device for breast inspection. Specifically, the
radiation tomography apparatus of Embodiment 2 generates a
tomographic image by imaging radiopharmaceutical distributed in the
breast B.
<Whole Construction of Radiation Tomography Apparatus>
FIG. 9 is a functional block diagram illustrating a detailed
configuration of a radiation tomography apparatus according to
Embodiment 2. A radiation tomography apparatus 9 according to
Embodiment 2 includes a gantry 11 with an opening configured to
insert a breast B of a subject M in a z-direction; and a detector
ring 12 in a ring shape provided inside the gantry 11 and
configured to insert the breast B of the subject M. The opening in
the detector ring 12 is cylindrical (strictly speaking, a regular
octagonal prism) extending in the z-direction. Accordingly, the
detector ring 12 itself extends in the z-direction. Here, the
opening of the detector ring 12 corresponds to a field of view
where the radiation tomography apparatus 9 allows generation of a
tomographic image P. The z-direction is in a direction where the
central axis of the detector ring 12 extends.
A top board 10 is provided for placing a subject M lying on her
stomach. The top board 10 includes a hole passing thereinto in the
z-direction for inserting the breast B of the subject M. Here, the
breast B is inserted through the hole into the detector ring 12.
The opening of the gantry 11 is directed upward vertically. Thus,
the breast B is to be inserted into the opening vertically toward a
lower side of the opening.
A shield plate 13 is composed of Tungsten or lead. See FIG. 9.
Since radiopharmaceutical exists in a portion of the subject M
other than the breast B, annihilation gamma-ray pairs are also
generated from the portion. Incidence of such the annihilation
gamma-ray pairs from the portion other than a site of interest into
the detector ring 12 causes obstruction of picking up a tomographic
image. Accordingly, the shield plate 13 in the ring shape is
provided so as to cover one end of the detector ring 12 adjacent to
the subject M in the z-direction.
A clock 19 sends time information with serial numbers to the
detector ring 12. The time information about time of detecting
gamma-rays is given to the detection signal outputted from the
detector ring 12, and then the signal is inputted into a
coincidence unit 20 to be mentioned later.
Description will be given of the detector ring 12. Eight radiation
detectors are arranged in a virtual circle on a plane orthogonal to
the z-direction (the central axis direction) to form a unit ring of
the detector ring 12. Three unit rings are arranged in the
z-direction to form the detector ring 12.
The detection signal outputted from the detector ring 12 is sent to
the coincidence unit 20 (see FIG. 9). Two gamma-rays incident on
the detector ring 12 simultaneously is an annihilation gamma-ray
pair derived from the radiopharmaceutical within the subject. The
coincidence unit 20 counts frequency of detecting the annihilation
gamma-ray pair for every combination of two scintillation counter
crystals constituting the detector ring 12, and the resultant is
sent to a tomographic image generating unit 22. Here, time
information that the clock 19 gives to the detection signal is used
for determination of coincident property of the detection signal
from the coincidence unit 20.
A data generating unit 21 generates space data D1 containing the
stereoscopic image of the breast of the subject M in accordance
with coincidence data outputted from the coincidence unit 20. The
tomographic-image generating unit 22 generates a tomographic image
P obtained when the opening of the detector ring 12 is cut along a
plane. The data generating unit 21 corresponds to the space-data
generating device in the present invention.
An image generating unit 23 expresses the body-surface identifying
unit 1, the body-surface intensity adjusting unit 2, and the MIP
image generating unit 3 in Embodiment 1 collectively.
A display unit 36 displays the tomographic image P and the MIP
image P1 generated by the tomographic image generating unit 22 and
the image generating unit 23, respectively. A memory unit 37 stores
all parameters, such as the detection signal outputted from the
detector ring 12, the coincidence data and the tomographic image P
generated by the coincidence unit 20 and the image generating unit
23, respectively, and the threshold. The parameters are referred to
upon operation of each unit.
Moreover, the radiation tomography apparatus 9 includes a main
controller 41 configured to control each section en bloc. The main
controller 41 has a CPU, and provides each of controllers 19, 20,
21, 22, and 23 by executing various programs. The above sections
may each be divided into a controller that performs their
functions.
<Operation of Radiation Tomography Apparatus>
Next, description will be given of operation of the radiation
tomography apparatus. Upon inspecting the breast B with the
radiation tomography apparatus 9 according to Embodiment 2, firstly
the subject M with radiopharmaceutical administered thereto by
injection in advance lies on his/her stomach on the top board 10
(subject placing step S1).
When adjusting a position of the subject M is completed, an
operator issues a command via a console 35 to start picking up a
tomographic image, whereby the detector ring 12 starts detection of
an annihilation gamma-ray pair (radiography starting step S2). The
tomographic-image generating unit 22 images the detected
annihilation gamma-ray pairs to generate a tomographic image P. On
the other hand, the image generating unit 23 images the detected
annihilation gamma-ray pairs to generate an MIP image P1. The
tomographic image P and the MIP image P1 are displayed on the
display unit 36 to complete operation of the radiation tomography
apparatus in Embodiment 2.
The construction as above allows provision of the radiation
tomography apparatus capable of obtaining the MIP image P1
representing the inside of the subject M accurately with no body
surface of the subject M appearing therein upon generating the MIP
image P1.
Typically, it is difficult to image breast cancer with use of
radiopharmaceutical. However, the present invention allows accurate
breast inspection since the MIP image P1 faithfully representing
the inside of the subject M is obtainable.
The present invention is not limited to the foregoing
configuration, but may be modified as follows.
(1) The body-surface intensity adjusting unit 2 sets the intensity
value of the body surface to 0. The present invention, however, is
not limited to this. That is, the body-surface intensity adjusting
unit 2 may substitute the intensity value of the body surface for a
value other than 0. In this case, the intensity value may be
substituted, for example, for a value lower than an average value
of the intensity values within the subject. This achieves
obtainment of intensity-corrected space data D2 with the structure
of the body surface remaining therein.
(2) The body-surface identifying unit 1 identifies the body surface
of the subject with the threshold p. The present invention,
however, is not limited to this. That is, the body surface of the
subject may be identified with use of a dynamic contour model such
as Snakes and a level set method.
(3) The above construction is for breast inspection. The present
invention, however, is not limited to this. That is, the present
invention is applicable to various types of PET apparatus such as
for inspection for a whole-body of a subject, inspection for a head
of a subject, and inspection for smaller animals.
(4) The above construction is applied to the PET apparatus. The
present invention, however, is not limited to this. The present
invention is applicable to other types of tomography apparatus,
such as a SPECT apparatus, an MIR apparatus, and a CT
apparatus.
(5) In each of the foregoing embodiments, the scintillation counter
crystal is composed of LYSO. Alternatively, the scintillation
counter crystal may be composed of another materials, such as LGSO
(Lu.sub.2(1-x)G.sub.2xSiO.sub.5) and GSO (Gd.sub.2SiO.sub.5), in
the present invention. This modification can provide a method of
manufacturing a radiation detector of low price.
INDUSTRIAL APPLICABILITY
As described above, the present invention is suitable for an image
processor for medical uses.
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